Load sensing variable displacement pumps are sometimes utilized for continuously driving a rotary motor wherein the displacement of the pump is controllably regulated to change the speed of the motor. The electrohydraulic pressure regulating valves commonly used for controlling the displacement of the pump typically have a fixed size orifice disposed upstream of a variable orifice. The upstream variable orifice can be defined by either a spool or a poppet type metering element with the displacement thereof being controlled by a solenoid. One of the problems encountered with the pressure regulating valves having a spool is the repeatability of the area control of the valve opening due to the quality of the solenoid and/or spool and to high flow forces acting on the spool caused by high pressure drops across the spool. A severe stability problem was encountered with the poppet type pressure regulating valves in this environment.
In view of the above, it would be desirable to provide an electrohydraulic pressure regulating valve in which the flow forces acting on the valving element are low to reduce sensitivity to solenoid and spool quality, has good pressure control capability, and is easily scaled based on orifice ratios.
The present invention is directed to overcoming one or more of the problems as set forth above.